Question

Glucose on oxidation with bromine water yields gluconic acid. This reaction confirms the presence of -

• A. six carbon atoms linked in straight chain
• B. secondary alcoholic group in glucose
• C. aldehyde group in glucose
• D. primary alcoholic group in glucose

Answer 1

The correct option is C

aldehyde group in glucose

Explanation for correct answer:-

Option (C) aldehyde group in glucose

• Oxidation of glucose in the presence of bromine water gives gluconic acid. The reaction confirms the presence of aldehyde group.
• Structure of Glucose:

• Structure of Gluconic acid:

• As we can see, the aldehyde group of glucose is oxidised into carboxylic group on oxidation with bromine water.
• Bromine water is a mild oxidising agent, in the presence of bromine water glucose is oxidised to gluconic acid which is a monocarboxylic acid with 6 carbon atoms.
• The overall reaction is represented below:

• The aldehyde group is oxidised. Therefore, reaction confirms presence of aldehyde group.
• Hence, the correct answer is option (C).

Explanation for incorrect answer:-

Option (A) Six carbon atoms linked in straight chain

• On oxidising glucose the six carbon ring is retained, only aldehydic group is oxidised.
• Hence, option (A) is incorrect.

Option (B) Secondary alcoholic group in glucose

• Since, on oxidation secondary alcoholic group in glucose is retained in Gluconic acid . Therefore, it cannot confirm the presence of secondary alcoholic group.
• Hence, option (B) is incorrect.

Option (D) Primary alcoholic group in glucose

• Both glucose and gluconic acid have primary and seconadry alcoholic group. Therefore on oxidation the presence cannot be confirmed.
• Hence, option (D) is incorrect.

Therefore, glucose on oxidation with bromine water yields gluconic acid. This reaction confirms presence of Option (C) aldehyde group in glucose.